hi, i have a valliant combi boiler, i turned the boiler off from the mains, drained the heating system out (to fit another radiator) filled it back up to 1.5 bars, bleed the rads, but i cant seem to get any hot water? the temperature needle was at 30, now its gone to 12? can anyone please help me.
To be honest, I would say that you can't link the boilers together as you suggest. In fact, I am sure you can't.
Firstly, when hot tap water is called for, the combi diverts the heating circuit to circulate the boiler water around a secondary heat exchanger. This means the water in the second boiler cannot circulate so may boil.
There is also going to be a control issue here too. How can you control both boilers to heat the water together? You will find one boiler has shut down thinking it has reached temperature while the other is thumping away trying to increase the temp.
The combi is not going to be happy either. There are known issues with trying to connect them in circuits which utilise solar energy. Condensing boilers use computer controls so damage could be caused if used outside the manufactures expectations.
The old boiler is probably designed to work only on a low pressure vented system so there will almost certainly be issues here too.
Last edited by plumbbob on Thu May 28, 2009 6:19 pm, edited 1 time in total.
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